Fuse unit having an operation indicator



Nov. 25, 1969 E. JACKS ETAL 3,480,901

FUSE UNIT HAVING AN OPERATION INDICATOR Filed Oct. 16, 1967 FIG.|

INVENTORS Eric Jacks and v Charles Rowe 7 BY Misegades 80 DouglasATTORNEYS United States Patent US. Cl. 337-244 3 Claims ABSTRACT OF THEDISCLOSURE A fuse unit having a striker pin operable upon rupture of thefusible element to eject a disc from the body of the fuse unit andprovide thereby an indication of this operation.

This invention relates to fuse units, and more particularly relates tofuse units having means for providing an indication of a fusible elementhaving ruptured.

Basically, the present invention consists in a fuse unit having astriker pin operable upon rupture of the fusible element to eject a discindicator from the body of the fuse unit and provide thereby anindication of its operation.

More particularly, the disc indicator may normally be held on the end ofthe fuse unit body by a spring clip or by frictional engagement, and inorder to limit the travel of the ejected disc it may be captively heldby a length of cord.

high voltage fuse units since such fuse units are frequently mounted inthe open at a considerable height from the ground which makes itdiliicult for a person standing at ground level to see whether or not afuse has blown, the visual indication hitherto having been thepenetration of the striker pin through the end cap of the fuse unit as aresult of the ignition of an explosive charge, or the release of aspring, upon the fuse element being ruptured.

A fuse unit according to this invention thus provides a more positiveand readily identifiable means of indicating a fuse which has blown, andthe design is such that it may readily be incorporated in existing fuseunits having striker pins without modification.

In order that the invention may be fully understood, two embodimentsthereof will now be described, by way of example, with reference to theaccompanying drawings, in which FIGURES 1 and 2 illustrate axialsections through two different forms of indicating members retained inposition on the end of a fuse unit.

Referring firstly to FIGURE 1, there is shown the end portion of a fuseunit having a striker pin 3 mounted with its head lying close to an endcap 4 secured to the tubular wall 5 of the fuse unit body. The end caphas a centrally disposed recess or well in which is secured a tubularspring clip 6 which itself grips an indicator disc 7. More particularly,the spring clip has a number of sharply pointed prongs 8 which extendoutwardly through windows" 9 so as to engage tightly the Walls of thewell and prevent withdrawal of the clip, and in addition includes anumber of inwardly extending fingers 10 which embrace an inner lip 11 onthe disc 7 and retain it in place.

This assembly thus ensures that the indicator disc cannot beaccidentally dislodged.

In operation, the rupture of the fusible element (not shown) results inthe striker pin being driven through the end cap whereupon it strikesand ejects the disc 7, thus affording an indication of the fuse havingblown.

In FIGURE 2 there is shown an arrangement similar to that in FIGURE 1,but in this case the indicating disc has an inwardly extending tubularwall 12 which engages the inner walls of the well. In addition, thetubular wall has a number of axially extending slots 13 formed therein,and it also accommodates a circlip 14 which outwardly biasses this wall12 against the inner walls of the well, thus ensuring the retention ofthe disc.

Again, upon rupture of the fusible element the striker pin is driventhrough the end cap whereupon it strikes and ejects the disc 7.

In order to prevent the ejected disc from falling onto adjacentapparatus or causing danger to personnel it may conveniently be retainedby a length of cord. The cord may be fastened between the disc and theend cap, and in the FIGURE 2 embodiment it may be secured to the circlip14 in the disc. Alternatively, instead of fastening the cord to the endcap it may conveniently be secured to another circlip located in thebase of the well and outwardly biassed against its walls.

The indication may be assisted by providing a coloured or reflectivematerial on the outer and/ or inner face of the disc, or on the faces ofthe well in the end cap so that it will be exposed when the disc isejected. The use of a reflective material in this manner willparticularly assist in the identification of a blown fuse in darkness.

The disc 7 may conveniently be made from a light plastics material, e.g.nylon, but in order to prevent the striker pin from piercing thismaterial a metallic plate may be located on the inner side of the discat the position of impact.

We claim:

1. In a fuse unit comprising a fusible element supported within atubular body of insulating material between two conductive terminals, astriker pin indicator comprising an end cap secured to one end of thebody and defining an axially recessed wall portion having a colored orreflective surface,

a striker pin housed within, and extending axially of the body, thestriker pin being secured to the fusible element under tension andoperable upon rupture of the element to be projected through one of theend caps,

a disc indicator frictionally secured within the recessed wall portionof the cap and lying in the path of travel of the striker pin whereby tobe ejected by the pin upon rupture of the fusible element and providethereby an indication of its operation, and

a length of cord secured at one end to the said end cap and to the saidindicator at the other end whereby to limit the length of travel of theindicator after its ejection.

2. A fuse unit according to claim 1, wherein the indicator is in theform of a shouldered disc and includes a spring clip outwardly biassingthe disc shoulders into frictional engagement with the recessed Wallportion of the cap.

3. A fuse unit according to claim 1, comprising a spring clip outwardlybiassed into frictional engagement with the recessed wall portion of thecap, the indicator being in the form of a plain disc held by said springclip.

References Cited UNITED STATES PATENTS 6/1915 Schweitzer et a1. 337-260X BERNARD A. GILHEANY, Primary Examiner 10 H. B. GILSON, AssistantExaminer US. Cl. X.R.

